A validation of margin of stability calculations relative to the pelvic coordinate system during gait

The margin of stability (MoS) is often quantified relative to an intended walking direction. This approach may not be suitable when the intended direction is altered, variable, or unknown. The purpose of this study was to describe and validate the approach of calculating the lateral minimum MoS relative to pelvic orientation. In straight-line walking, the pelvic-oriented MoS was smaller, yet more variable than the typical calculation. For curved-path walking, a condition representing an exaggerated trajectory departure, the pelvic-oriented MoS was different and less variable than that calculated in the global coordinates.